Hundreds of schools have banned their teachers from marking in red ink in case it upsets the children. They are scrapping the traditional method of correcting work because they consider it "confrontational" and "threatening".
Pupils increasingly find that the ticks and crosses on their homework are in more soothing shades like green, blue, pink and yellow or even in pencil.
Traditionalists have condemned the ban sweeping classrooms as "absolutely barmy", "politically correct" and "trendy".
They insist that red ink makes it easier for children to spot errors and improve.
The red pen goes back further than most schools, having been developed during the mid-19th century when ammonia-based dyes became available.
But the opposition to using red ink is now a worldwide trend with recent guidelines to schools in Queensland, Australia warning that the colour can damage students psychologically.
There are no set guidelines in this country on marking, and schools are free to formulate their own individual policies.